Dosing unit for an ambulatory infusion device

ABSTRACT

A dosing unit for an infusion pump device is disclosed having a piston pump with a pump cylinder and a plunger arranged within said cylinder, coaxially arranged along a longitudinal axis. The plunger has a shaft with a thread and the cylinder has a threaded sleeve part with a thread. The two threads engaging with each other in such a way that a rotational movement of the plunger around the longitudinal axis results in an additional linear displacement of the plunger along said longitudinal axis. A separate bias force element biases the two threads in regard to each other along the longitudinal axis, such that the threaded engagement of inner thread and outer thread is free of play independent of a direction of a rotational movement and linear displacement of the plunger in regard to the cylinder.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/193,074, filed Feb. 28, 2014, which is a continuation ofInternational Application No. PCT/EP2012/065972, filed Aug. 15, 2012,which claims priority to International Application No.PCT/EP2011/065242, filed Sep. 2, 2011, which are herein incorporated byreference in their entirety.

TECHNICAL FIELD

The invention relates to dosing units for infusion pump devices, andinfusion pump devices with such a dosing unit.

BACKGROUND

Devices for the automated release of liquid medicaments are normallyused with patients who have a continuous and in the course of the dayvarying need of a liquid medicine which can be administered by infusion.Specific applications are, for example, certain pain therapies, cancertherapies and the treatment of diabetes mellitus, in which computercontrolled infusion pump devices are used. Such devices are particularlyuseful for ambulatory therapy, and are generally carried attached on ornear the body of a patient. The medicine reservoir often comprisesmedicine supply sufficient for one or several days. The liquidmedicament is supplied to the patient's body from the medicine reservoirthrough an infusion cannula or an injection needle.

Ambulatory infusion pump devices are typically of the syringe drivertype, where the liquid medicament to be administered to the patient isstored in a cylindrical glass cartridge or ampoule acting as the liquidmedicament reservoir, and is conveyed to the body of the patient bydisplacing a plunger within the cylinder. An example of such an infusionpump device is disclosed for example in WO 01/83008 A1. A cylinder ofthe dosing unit comprises the complete reservoir of liquid medicament ofthe infusion pump device. A plunger plug arranged in the cylinder isunidirectionally displaced along the cylinder axis by a drive system viaa shaft or threaded spindle.

EP 2163273 A1 of the applicants, the disclosure of which is herebyincluded by reference in its entirety, discloses a piston pump baseddosing unit for an Infusion pump device with a 4/3 or 3/3 way valvesystem arranged at a front end of the cylinder of the dosing unit. Aplunger arranged in the cylinder of the dosing unit can thebidirectionally displaced along the cylinder axis by a spindle drivesystem. In one state of the valve, an inlet conduit fluidly connected tothe primary reservoir is fluidly connected to the cylinder cavity, andan outlet conduit fluidly connected to the infusion tubing isdisconnected from the dosing unit. This state of the valve is appliedduring the refill mode, when the dosing unit retracts the plunger andsucks liquid medicament from the primary reservoir into the pumpcylinder/secondary reservoir. In a second state of the valve, thecylinder of the dosing unit is fluidly connected to the outlet conduit,thereby establishing a fluid connection to the body of the patient. Theinlet conduit is disconnected from the dosing unit. This valve state isapplied during the pump mode, when liquid medicament is conveyed fromthe secondary reservoir in the cylinder of the dosing unit to thesubcutaneous tissue of the patient. The valve thus either allows thedosing unit to retrieve liquid from the primary reservoir, or to conveyliquid from the secondary reservoir of the dosing unit toward thepatient.

The valve is realized as a rotatable cylinder acting as a valve member,mounted in a fixed valve seat. The cylinder member of the valve isfrictionally connected to the plunger. By rotating the plunger along thecylinder axis, the actuating means of the plunger indirectly actuatealso the valve member, by rotating the cylinder/valve member within thestationary valve seat. Thus no separate actuator is needed for thevalve. Furthermore the valve system and the piston pump are coupled suchthat in the pump mode, the valve will automatically be in the pumpstate, and in the refill mode, the valve will automatically be in theretrieving state. Thus also no additional control means is needed forthe valve.

In order to rotate the cylinder and to switch the valve, the plunger hasto exert a rotational torque on the cylinder member. At the same timethe rotational torque exerted on the plunger by a drive unit has to betranslated into a linear displacement of the plunger along the cylinderaxis. For that purpose the plunger shaft is provided with an outerthread that interacts with an inner thread provided on the cylinder. Thedosing unit is designed such that the static frictional force betweenplunger and cylinder member (including friction between plunger plug andcylinder wall and friction of the thread) is larger than the staticfriction between cylinder member and valve seat. When the drive unitrotates the shaft into one direction, the cylinder is frictionallycoupled to the rotating plunger and rotates in the valve seat untilfinally reaching an end position, where its further rotation ismechanically blocked by a stopper. The plunger is now frictionallydecoupled from the cylinder member, and any further rotation of theplunger is translated by the threads into a linear displacement alongthe cylinder axis. When the rotation of the plunger is reversed, thecylinder member is no longer rotationally blocked in the valve set, andplunger and cylinder member are frictionally coupled again. The cylindermember thus rotates in the valve seat in the reverse direction, actuatedby the drive unit via the plunger, until a second stopper is reached,corresponding to the second valve state. The plunger is decoupled againfrom the blocked cylinder member, and is now linearly displaced alongthe cylinder axis in the opposite direction. The design of such acombined piston pump/valve system is named “valve before plunger”design, since the valve is actuated before the plunger is actuated.

In an infusion pump device as discussed above, all parts that come intocontact with liquid medicament, as well as parts that are subject tofriction, may be arranged in a disposable subunit. Prior to use of theinfusion pump device, a fresh disposable subunit is coupled to areusable subunit, comprising for example the electronics, the drivesystem, the battery, and all other parts that are not prone tocontamination or wear, and can be used over a longer time period.

Since the spindle that actuates the plunger of the pump is typicallymade from a polymer material, and thus would be subject to wear if usedover a long time period, it is advantageously also part of thedisposable subunit. However, if a simple threaded rod coupled to theplunger would be used as the spindle of the spindle drive, the length ofthe disposable subunit would depend on the plunger position. Such adesign would complicate the coupling of the disposable subunit to thereusable subunit, namely the coupling of the spindle to the drive motor.

In the dosing unit shown in EP 2163273 A1, the length of the disposablesubunit is hold constant. The plunger spindle of the dosing unitcomprises a plunger shaft attached to the plunger, and a coaxial plungerdriving rod arranged in a longitudinal bore along its axis of theplunger shalt. The driving rod can be linearly shifted along thelongitudinal bore. The cross-section of the driving rod and thelongitudinal bore are chosen such that a rotational torque iseffectively transmitted from the driving rod to the plunger shaft. Thecoupler element can be coupled to a driving unit of a reusable subunit.The linear displacement of the plunger during the spindle actuation iscompensated by the two-part spindle. While the plunger shaft is linearlyshifted together with the plunger, the driving rod remains on place inregard to the drive unit. The transmission of the rotational torque fromthe drive unit to the plunger shaft is effected by the rotationalcoupling between plunger shaft and driving rod.

A spindle drive, as it is also present in the above-referenced dosingunit, unavoidably has a certain thread lash. When spindle rotation isreversed, the flanks of the inner thread and the outer thread areslightly shifted in regard to each other along the longitudinal axis. Ina standard single-reservoir syringe-type infusion pump, thread lash isnot relevant, since the spindle drive in unidirectional. Thus afterpriming of the pump system there is no reversal of the spindle rotationdirection. Thread lash can be potentially detrimental to meteringprecision for secondary-reservoir piston pump dosing units, where therotation direction is repeatedly reversed after priming. After switchingthe rotational direction of the plunger, for a small rotation angle ofthe plunger the threads are not coupled, resulting in a rotation of theplunger without linear displacement. Furthermore the linear forceexerted on the plunger may have to counteract an opposite force due to apressure differential in the cylinder cavity. Depending on thecircumstances this can lead to a small linear displacement of theplunger within the cylinder, without rotation. As a result, the meteringprecision of such a dosing unit may be restricted.

This precision reducing effect of the thread lash is particularlyrelevant when the rotation angle and/or the linear displacement of theplunger are used to determine the position of the plunger plug withinthe cavity and/or the volume of retrieved/conveyed liquid volume.Although such a metering measurement method is very precise, and cantake into account various effects, it cannot counterbalance thread lash,since thread lash cannot be detected such a method.

Counter spindle drives are used to avoid thread lash in high precisionlinear motors, for example for machining devices such as lathes.However, such complex drives are not applicable for infusion pumpdevices, since they are too voluminous and complex.

SUMMARY

In at least one embodiment of the present disclosure, a dosing unit foran infusion pump device is disclosed. In an exemplary embodiment, adosing unit for an infusion pump device comprises a piston pump with apump cylinder and a plunger arranged within said cylinder, coaxiallyarranged along a longitudinal axis. The plunger has a shaft with athread and the cylinder has a threaded sleeve part with a thread. One ofthe two threads is an outer thread and the other one is an inner thread,said two threads engaging with each other in such a way that arotational movement of the plunger around the longitudinal axis resultsin an additional linear displacement of the plunger along saidlongitudinal axis. A separate bias force element biases the two threadsin regard to each other along the longitudinal axis, such that thethreaded engagement of inner thread and outer thread is free of playindependent of a direction of a rotational movement and lineardisplacement of the plunger in regard to the cylinder. The plungerthread may optionally be an outer thread and the cylinder thread may bean inner thread.

In at least one embodiment of the dosing unit, the bias force elementsubjects the plunger shaft to a force perpendicular to the longitudinalaxis, thereby pressing a portion of the plunger thread onto a portion ofthe cylinder thread. Such a bias force element may comprise a radiallybiased flat surface that abuts the lateral surface of an outer one ofthe two threads.

In at least one embodiment of the dosing unit, one or more portions ofthe cylinder thread or the plunger thread are pivotably mounted on thecylinder, or on the plunger shaft, respectively. Additionally, a springelement may also be included in the dosing unit. The exemplary springelement may be a tension ring, which radially biases the pivotablymounted thread portions toward the other thread.

In at least one embodiment of the dosing unit, the bias force elementcomprises a tensioned segment of wire that is mounted to the cylinder orthe plunger and is arranged in such a way that it is located in a groovesegment of the outer thread and exercises a bias force perpendicular tothe longitudinal axis.

In at least one embodiment of the dosing unit, the bias force elementcomprises a threaded element, which is coaxially mounted on the firstthreaded sleeve or on the plunger shaft, and is longitudinally shiftablein regard to the first threaded sleeve or the plunger shaft,respectively. The threaded element has a thread portion engaging withthe plunger thread or the cylinder thread, respectively. Further thethreaded element may have a spring element that subjects the threadedelement to an axial bias force in regard to the first threaded sleeve orthe plunger shaft, respectively.

In at least one embodiment of the dosing unit, the bias force elementcomprises one or more spring elements with inner or outer threadsegments, such that said inner or outer thread segments are radiallybiased toward the outer or inner thread. The inner or outer threadsegments act as the inner or outer thread, respectively. In at least oneembodiment of the present disclosure, the bias force element is elastic.

The bias force element, in at least one embodiment, is made from amaterial that is different from the material of the cylinder and/or theplunger. Further, the bias force element can be made from metal, andalternatively or in addition the cylinder and/or the plunger can be madefrom polymer.

In at least one embodiment of the dosing unit, the plunger driving partis provided for transmitting rotational torque from a driving unit tothe plunger without itself being linearly displaced. The cylinder, theplunger and the plunger driving part are coaxially arranged along alongitudinal axis and are rotatable around said axis in regard to staticparts of the dosing unit. The plunger has a shaft with a thread and thecylinder has a threaded sleeve part with a thread. One of the twothreads is an outer thread and the other one is an inner thread, saidtwo threads engaging with each other in such a way that a rotationalmovement of the plunger around the longitudinal axis results in anadditional linear displacement of the plunger along said longitudinalaxis. The plunger driving part has a driving rod that is arranged in alongitudinal bore of the plunger shaft, the driving rod being linearlydisplaceable within the longitudinal bore along the longitudinal axis,and being rotationally engaged with the plunger shaft.

In at least one embodiment of the present disclosure, the one or morefirst coupling parts are mounted to or integral with the cylinder, andthe one or more second coupling parts are mounted to or integral withthe plunger driving part and/or the plunger. The first and secondcoupling parts interact in such a way that upon a reversal of therotation direction of the plunger driving part the cylinder isrotationally coupled to the plunger driving part if it was previouslynot rotationally coupled, and vice versa. Alternatively, or in addition,the one or more first coupling parts may be mounted to or integral withthe cylinder and/or the plunger driving part, and one or more secondcoupling parts are mounted to or integral with the plunger driving partand/or the plunger. The cylinder is rotationally coupled to the plungeron certain linear positions of the plunger in regard to the cylinder andbeing not rotationally coupled to the plunger on the other position.

In at least one embodiment of the dosing unit of the present disclosure,the coupling parts may, at least partly, be part of the plunger drivingpart and do a direct (selective) torque transmission from the plungerdriving part to the cylinder. Alternatively the coupling parts may, atleast partly, be part of the plunger and do an indirect (selective)torque transmission from the plunger driving part to the cylinder, viathe plunger. The plunger driving part is distinct from both cylinder andplunger.

In at least one embodiment of the present disclosure, the plungerdriving part receives a rotational torque from some drive and providesthat torque either to the plunger only (decoupled state) or to bothplunger and cylinder (coupled state). The plunger driving part mayfulfils the functions of transforming a pure rotational drive movementinto a screw-like combined rotational and linear movement of theplunger, and selectively rotationally coupling the cylinder to thedrive.

In at least one embodiment of the present disclosure, the dosing unithas reduced energy consumption, since the cylinder can be decoupled fromthe drive unit, as long as the valve does not have to be switched.

In at least one embodiment of the present disclosure, the one or morefirst coupling parts are mounted to or integral with the cylinder, andone or more second coupling parts are mounted to or integral with theplunger driving part and/or the plunger. The first and second couplingparts may interact in such a way that the first and second couplingparts are bidirectionally switchable between a first state and a secondstate, by reversing the rotation direction of the plunger driving pan;the first and second coupling pans are unidirectionally switchable fromthe first state to the second state, by mechanically blocking cylinderrotation or actuating the first coupling part; and the cylinder isrotationally coupled to the plunger driving part in the first state ofthe first and second coupling parts; and not rotationally coupled in thesecond state.

In at least one embodiment of the present disclosure, a first couplingpart is mounted to or is integral with the cylinder, and a secondcoupling part is mounted to or is integral with the plunger drivingpart. The first and/or the second coupling parts may comprise one ormore bistable elements that can be in a first configuration where thebistable elements rotationally couple the first and second couplingparts by static friction or positive locking when the plunger drivingpart rotates clockwise, and do not rotationally couple the first andsecond coupling parts when the plunger driving part rotatescounter-clockwise. In a second configuration the bistable elementsrotationally couple the first and second coupling parts by staticfriction or positive locking when the plunger driving part rotatescounter-clockwise, and do not rotationally couple the first and secondcoupling parts when the plunger driving part rotates clockwise.

In at least one embodiment of the present disclosure, the bistableelements are friction elements that are switchable between twoconfigurations, and that the rotational coupling is a static frictionalcoupling. Further, the bistable friction elements may be switchablebetween the two configurations by reversing the rotation direction ofthe plunger driving part in case the first and second coupling parts arenot rotationally coupled; and by reversing the rotation direction of theplunger driving part and blocking cylinder rotation in case the firstand second coupling parts are rotationally coupled. Additionally, thecylinder rotation may be blocked on certain angular orientations of thecylinder in regard to the static parts of the dosing unit.

In at least one embodiment of the dosing unit, where the first andsecond coupling parts are unidirectionally switchable front a firststate to a second state, by mechanically blocking cylinder rotation,such a change occurs, more generally spoken, if the torque for rotatingthe cylinder exceeds a maximum torque that can be transmitted via thecoupling from the bistable friction elements to the cylinder. In atleast one embodiment, such a change occurs only in the mechanicallyblocked state, where the torque for further rotating the cylinderbecomes essentially infinite.

The bistable elements may also be ratchet mechanisms that are switchablebetween two configurations, and that the rotational coupling is givenwhen the ratchet mechanism is locked. Additionally, the bistable ratchetmechanisms may switchable between the two states by reversing therotation direction of the plunger driving part in case the ratchetmechanism is locked; and by reversing the rotation direction of theplunger driving part and additionally actuating the ratchet mechanism incase the ratchet mechanism is not locked. In at least one embodiment,the ratchet mechanism is actuated by switching elements mounted to orbeing integral with the static parts of the dosing unit.

In at least one embodiment of the present disclosure, one or more firstcoupling parts are mounted to or integral with the cylinder and/or theplunger driving part, and one or more second coupling parts are mountedto or integral with the plunger driving part and/or the plunger. Thefirst and second coupling parts may interact in such a way that thecylinder is rotationally coupled to the plunger on certain linearpositions of the plunger in regard to the cylinder and is notrotationally coupled to the plunger on the other positions.

In at least one embodiment of the present disclosure, the first couplingparts comprise first ramps provided on the plunger driving rod, and thesecond coupling parts comprise second ramps provided on a structurepivotably mounted on the plunger shaft. The structure carries portionsof the outer thread. The first and second ramps are arranged such thaton certain linear positions of the plunger in regard to the cylindersome of the first ramps abut some of the second ramps, and press theouter thread portions radially outwards onto the inner thread of thecylinder, thereby frictionally coupling the cylinder and the plunger.

In at least one embodiment of the present disclosure, the one or morefirst coupling parts are first friction elements mounted to or beingintegral with the cylinder, and the one or more second coupling partsare second friction elements mounted to or being integral with theplunger. At certain longitudinal positions of the plunger in regard tothe cylinder one of the first friction elements frictionally engageswith one of the second friction elements, thereby frictionally couplingthe cylinder and the plunger. Further, the one or more first frictionelement may be a hollow cylinder, and the one or more second frictionelement may be a friction cylinder, which frictionally engages with thehollow cylinder when the friction cylinder is located in the hollowcylinder.

In at least one embodiment of the present disclosure, the one or morefirst coupling parts are first stopper elements mounted to or beingintegral with the cylinder, and the one or more second coupling partsare second stopper elements mounted to or being integral with theplunger. In at least one longitudinal position of the plunger in regardto the cylinder one of the first stopper elements abuts with one of thesecond stopper elements, thereby blocking the further lineardisplacement of the plunger, and releasably jamming the inner thread ofthe cylinder and the outer thread of the plunger. The stopper elementsare in at least one embodiment may be disks.

In at least one embodiment of the present disclosure, the dosing unithas a cylinder coupling part as the first coupling part and a plungercoupling part as the second coupling part. The cylinder coupling partcomprises first locking elements and the plunger coupling part comprisessecond locking elements, which releasably lock the plunger to thecylinder at certain longitudinal positions of the plunger in regard tothe cylinder.

In at least one embodiment of the present disclosure, the one or morefirst coupling parts are mounted to or being integral with the cylinder,and one or more second coupling parts are mounted to or being integralwith the plunger driving part. The tint and second coupling parts in atleast one embodiment interact in such a way that the cylinder isrotationally decoupled from the plunger driving part on certain angularorientations of the cylinder in regard to static parts of the dosingunit, and is rotationally coupled on the other orientations.

In at least one embodiment of the present disclosure, the first couplingpart is mounted to or Is integral with the cylinder, and a secondcoupling part is mounted to or is integral with the plunger drivingpart. The two coupling parts are frictionally coupled. The frictionalcoupling is releasable by switching elements mounted to or beingintegral with the static parts of the dosing unit.

In at least one embodiment, an infusion pump device according to thedisclosure comprises a dosing unit according to the disclosure.

DRAWINGS

The features and advantages of the present disclosure, and the manner ofattaining them, will be more apparent and better understood by referenceto the following descriptions taken in conjunction with the accompanyingfigures, wherein:

FIG. 1 schematically shows a possible embodiment of a dosing unitaccording to at least one embodiment of the disclosure, (a) in alongitudinal section along the cylinder axis, and (b) in a cross sectionthrough the plunger shaft and the plunger driving rod along plane A-A.

FIG. 2 schematically shows a detail view of at least one embodiment of athread lash reducing arrangement as shown in FIG. 1.

FIG. 3 schematically shows at least one embodiment thread lash reducingarrangements in a dosing unit according to the present disclosure.

FIG. 4 depicts at least one embodiment of an dosing unit of the presentdisclosure without thread lash, with a ring-like metal spring element asa radial bias element, (a) in a top view, (b) in a longitudinal sectionalong plane B-B, and in a cross-section along plane A-A, (c) with theplunger shaft, and (d) without the plunger shaft. The plunger is shown(e) without the plug sealing element material in top view, (f) in across-section along plane C-C, and (g) in side view with view along thelongitudinal axis on the bore. The radial bias force element is shown in(h).

FIG. 5 depicts at least one embodiment of a dosing unit, with aring-like metal spring element as a radial bias element, (a) in topview, (b) in a longitudinal section along plane A-A, and (c) in across-section along plane B-B. The radial bias force element is shown in(d).

FIG. 6 schematically shows a further embodiment of a radial bias forceelement, (a) in a longitudinal view on the split end of the plungershaft, and (b) in a side view on the end of the plunger shaft.

FIG. 7 depicts at least one embodiment of a plunger according to thepresent disclosure with thread lash reduction, having three pivotablymounted thread portions, (a) in a perspective view, (b) in alongitudinal view, (c) in a longitudinal section along plane A-A, and(d) in a cross-section along plane B-B.

FIG. 8 shows at least one embodiment of a thread lash reductionarrangement according to the present disclosure, with four threadedclaws at the distal end of the cylinder engaging with a threaded plungershaft, (a) in a side view with view on the distal end, and (b) in alongitudinal section along plane A-A.

FIG. 9 schematically depicts at least one embodiment of a dosing unitwith thread lash reduction arrangement, in which three biased springelements act as an radially biased outer thread, with the dosing unit(a) in a perspective view, and (b) in a detail view of a longitudinalsection, with a distal sleeve (c) in a longitudinal view, and (d) in aperspective view, and with an axial bias force element with threeradially biased spring elements (e) in a longitudinal view, and (f) in aperspective view.

FIG. 10 shows at least one embodiment of a thread lash reductionarrangement according to the present disclosure, in which a biased wireis used as a radial bias force element. The interaction of the biasedwire, the threaded plunger shalt, and the thread portion on the cylindersurface is schematically depicted in (a). A distal portion of thecylinder is shown in (b), and a cross-section along plane A-A in (c).

FIG. 11 shows at least one embodiment of a thread lash reductionarrangement according to the present disclosure, with an axially biasedthreaded sleeve, (a) in a longitudinal section though plunger shaft,threaded sleeve and axial bias force element, and (b) in a schematicaldetail view of the interacting thread portions, (c) discloses yet afurther variant of a thread lash reduction arrangement, with an axiallybiased threaded plunger shaft, a longitudinal section through plungershaft, threaded sleeve and axial bias force element.

FIG. 12 schematically shows a longitudinal section of at least oneembodiment of a dosing unit with controlled friction between plunger andcylinder, (a) with the plunger in a start position, (b) with the plungerin a medium position, and (c) with the plunger in a maximum position. Adetail of FIG. 12(a) is shown in (d), explaining how the driving rodcontrols the friction between plunger and cylinder.

FIG. 13 schematically shows the plunger of FIG. 12, (u) in alongitudinal section along plane A-A, (b) in a cross-section along planeB-B, and (c) in a cross-section along plane C-C.

FIG. 14 schematically shows the driving rod of FIG. 12, (a) in a sideview, (b) in a top view, and (c) in a cross-section along plane D-D.

FIG. 15 schematically shows a longitudinal section of at least oneembodiment of a plunger shaft and driving rod that allows valveswitching in intermediate positions according to the present disclosure.

FIG. 16 schematically shows at least one embodiment of a dosing unitwith controlled friction between plunger and cylinder according to thepresent disclosure, (a) with the plunger in a start position, and (b)with the plunger in a maximum position. A detail of FIG. 16(a) is shownin (c), explaining how the driving rod controls the friction betweenplunger and cylinder.

FIG. 17 schematically shows at least one embodiment of a dosing unitwith controlled friction between plunger and cylinder, (a) with theplunger in a start position, and (b) with the plunger in a maximumposition. A detail of FIG. 17(a) is shown in (c), explaining how thedriving rod controls the friction between plunger and cylinder.

FIG. 18 schematically shows at least one embodiment of a dosing unit ofthe present disclosure with controlled friction between plunger andcylinder, (a) with the plunger in a start position, and (b) with theplunger in a maximum position.

FIG. 19 schematically shows at least one embodiment of a dosing unit ofthe present disclosure with controlled friction between plunger andcylinder, and thread lash reduction, with the plunger in an intermediateposition.

FIG. 20 schematically depicts a longitudinal section of at least oneembodiment of a dosing unit of the present disclosure, in which thecylinder is positively locked to the plunger at certain longitudinalpositions, (a) with the plunger in a start position, (b) with theplunger in a medium position, and (c) with the plunger in a maximumposition.

FIG. 21 schematically depicts at least one embodiment of a dosing unitof the present disclosure: (a) in a longitudinal section with theplunger in a start position, (b) in a longitudinal section perpendicularwith the plunger in a maximum position, (c) in a detail view of (a), and(d) in a detail view of (b).

FIG. 22 schematically depicts a longitudinal section of at least oneembodiment of a dosing unit or the present disclosure with the plungerin the start position, in which the cylinder can be releasablypositively locked to the plunger at certain longitudinal positions.

FIG. 23 schematically shows at least one embodiment of a coupling systemof the present disclosure that allows switching the valve of a dosingunit at any longitudinal position of the plunger, (a) in a crosssection, and (b) to (e) in detail views of different steps during thevalve switching.

FIG. 24 schematically shows at least one embodiment of a coupling systemof the present disclosure that allows switching the valve of a dosingunit at any longitudinal position of the plunger, (a) in a bottom viewof the driving rod, (b) in a side view of the driving rod, and (c) in adetail of a cross-section of the coupling part of the driving rodcoupled to the cylinder wall, (d) to (g) show detail views of differentsteps during the valve switching.

FIG. 25 schematically shows cross-sections of at least one embodiment ofplunger shafts and driving rods, (a) without and (b) to (d) withrotational play.

FIG. 26 shows a perspective view of at least one embodiment of a dosingunit with the cylinder/plunger combination with thread lash reductionarrangement as shown in FIG. 5, and with a cylinder/driving rod couplingarrangement similar to FIG. 24.

FIG. 27 shows the different steps during valve switching with the dosingunit of FIG. 26.

FIG. 28 schematically shows subsequent steps of at least one approach torealize a controlled coupling between cylinder and driving rod, based ona bistable ratchet mechanism.

FIG. 29 schematically shows at least one embodiment of a controlledcoupling between cylinder and driving rod, (a) in a perspective view onthe interacting coupling parts, and (b) in a perspective view of thecylinder coupling part alone.

DETAILED DESCRIPTION

A dosing unit without thread-lash is advantageous for several reasons.The metering precision is increased due to the reduction of meteringerrors due to uncontrolled plunger displacement. Furthermore theseparation in time of the valve switching process and the plungerdisplacement process is more precise, since the thread friction force,adding to the friction force between cylinder valve member and plunger,remains essentially constant when the plunger rotation direction isreversed.

A self-biasing polymer plunger shall for thread-lash reduction has thedisadvantage that its bias force deteriorates over time in anirreproducible manner, which eventually reduces the acceptable shelftime of a disposable dosing unit prior to first use in an ambulatoryinfusion pump device. In an advantageous dosing unit according to thisdisclosure, a separate bias force element is provided, thereby allowingusing a plunger without detrimental mechanical stress.

At least one embodiment of a dosing unit 1 according to the presentdisclosure is schematically depicted in FIG. 1. A cylinder valve member2 is rotatably mounted in a stationary valve seat 12. A plunger 3 with aplug 31 and a shaft 32 is arranged in the cylinder 2. The plunger plug31 sealingly closes the cylinder, thereby defining a metering cavity 11between the cylinder head 21 and the plug. In the figure, the valveformed by the valve seat 12 and the cylinder valve member 2 is in one ofits two operational valve states, where an inlet 121 is fluidlyconnected to the metering cavity 11 through an opening 211 in thecylinder head. The inlet 121 is fluidly connected to a primary reservoirof an infusion pump device (not shown). A downstream outlet 122 towardan infusion set (not shown) is disconnected from the metering cavity 11.

The plunger plug 31 is attached to a plunger shaft 32, which is providedwith an outer thread 33 that interacts with an inner thread 23 arrangedon the cylinder. The plunger shaft 32 is provided with a longitudinalbore 322 along its axis, having a square cross-section, in which a rod41 of a plunger driving part 4 is arranged. The plunger driving rod 41has a square cross-section corresponding to the longitudinal bore 322 ofthe plunger shaft. Thus the rod 41 can be shifted with only minimumfriction in the longitudinal bore 322, while at the same timeefficiently transmitting a rotational torque around the axis 20 from theplunger coupler to the plunger 3. Plunger shaft and plunger driving rodare designed such that the bore 322 is vented toward atmosphere.

The plunger shaft 32 and the plunger driving rod 41 together form theplunger spindle of the dosing unit. The plunger driving part 4 isrotationally coupled to a driving unit of the infusion pump device (notshown). In case the dosing unit is designed as a disposable element,which is intended to be replaced in regular intervals, the plungerdriving part is advantageously provided with a drive unit coupling 42for releasably coupling the plunger coupler to the drive unit. Duringoperation, the drive unit (not shown) exerts a rotational force on theplunger coupler via the drive unit coupling 42, and the plunger couplertransmits this rotational torque to the plunger 3. While the plungerdriving rod remains stationary along the longitudinal axis, the plungeris linearly displaced along the axis.

Since the frictional coupling between plunger and cylinder is largerthan between cylinder and valve seat, the plunger is frictionallycoupled to the cylinder member, as long as the cylinder has not yetrotated to a blocking position, corresponding to an operational valvestate. In the blocking position of the valve, the now decoupledrotational movement of the plunger is translated into a linear movementof the plunger, by the spindle drive realized by the outer thread 33 ofthe plunger and the inner thread 23 of the cylinder.

In at least one embodiment shown in FIG. 1, the thread lash is minimizedby an advantageous thread lash reduction arrangement. The inner threadof the cylinder is realized as a single thread segment 23 having asegment angle of 180° or less. A separate radial bias force element 5 isprovided on the cylinder wall, on the side opposite to the inner threadsegment 23. Said bias force element 5 is realized in the givenembodiment with a radially biased flat surface element 56 pressing onthe outer thread 33 of the shaft 32, thereby pressing the outer thread33 on the opposite side of the shaft radially onto the thread segment23. A defined bias force is generated by a spring element 52 or othersuitable resilient element, which in the figure is shown onlyschematically.

The principle of the applied thread lash reduction arrangement is shownin more detail in FIGS. 2(a) and (b), schematically depicting alongitudinal section through a portion of a plunger shaft 32 with outertrapezoid thread 33, interacting with a trapezoid thread segment 23 onthe cylinder wall 22. On the opposite side of the thread segment 23, aradial bias force element 5 is arranged, exerting a radial bias forceF_(bias) perpendicular to the cylinder axis 20. The radial bias forceelement 5 is here realized as a flat element 56, abutting the outersurface 331 of the spindle 32, 33, and biased by a helical spring 52.The bias element exerts a radial force on the outer thread 33 surfaceand the shaft 32, without directly interacting with the thread 33. As aresult, there is a radial force F_(bias) between thread 33 and threadsegment 23, resulting to which the two threads closely abut each other,without a thread lash. Thus with at least one exemplary arrangementthere will be no undefined plunger motion upon reversal of the rotationdirection, or pressure differentials in the metering chamber.

The parameters of at least one exemplary thread as such, namely threadform, flank angle, and helical angle are mainly defined by the intendedapplication, namely a self-locking spindle drive. With a thread having aflank angle α, and neglecting the comparably small helix angle of thethread, an axial force F_(ax) acting on the plunger shaft 32 will have aforce component F_(a)=cos(α)F_(ax) parallel to the surface of the threadflank. Similarly there acts a force component F_(b)=sin(α)F_(bias)parallel to the flank surface, in the opposite direction. Thus as longas biasing force component F_(b) is larger than an axial force componentF_(a) exerted on the plunger, or sin(α)F_(bias)>cos(α)F_(ax), the axialforce cannot overcome the bias force, and the outer thread flank cannotslide along the flank of the thread segment 23, which would lead to aaxial shift of the plunger.

In at least one embodiment, the biasing force should be properlyadjusted to avoid increased thread friction, and tints for the batterylife time of a corresponding infusion pump device.

The maximum axial force F_(ax,max) that may occur on the plunger duringnormal operation can be estimated. Based on that upper limit anappropriate minimum radial force of the bias force element isdetermined, as F_(bias,min)=cot(α)F_(ax). The smaller the flank anglethe smaller is thread friction during operation, which is advantageousin regard to energy consumption. On the other hand it considerablyincreases the necessary bias force. An advantageous compromise in adosing unit according to the disclosure is for example a trapezoidthread with flank angle 60° (cot 60°=0.58) and helical angle 3.4°.

In at least one embodiment, the bias force is generated by a springelement, for example a metal helical spring. Other types of resilientelements are possible. The material of the resilient element is chosensuch that it does not deteriorate over time in regard to the springforce, thereby allowing a long shelf time prior first use.

The plunger shaft and the cylinder wall including thread segment 23 ofat least one embodiment may be manufactured from a thermoplastic polymermaterial compatible for medicinal applications. It should furthermoreprovide elasticity parameters suitable for application in self-lockingspindle drives. Exemplary materials that may be used in at least oneembodiment include for example poly-amide (PA), polypropylene (PP),methyl methacrylate butadiene styrene terpolymer (MBS), and polybutyleneterephthalate (PBT).

At least one embodiment of a thread lash reducing arrangement is shownin FIG. 3(a), where the bias force element 5 is realized as a biasedthread segment 51, interacting with the outer thread 33. A furtherembodiment is shown in FIG. 3(b), where three parallel thread segments23 are provided. Such a variant with more than one thread flankinteracting is less advantageous than the variants discussed before,since the actual forces acting on the thread can be determined lessprecisely due to manufacturing tolerances.

At least one embodiment of a dosing unit of the present disclosure isdisclosed in FIG. 4. The pump cylinder/valve member 2 comprises twoparts 28, 26, and is rotatably arranged in the valve seat 12. Theplunger plug 31 is arranged in a proximal (proximal meaning “toward thevalve”) cavity part 28 of the cylinder, together defining the variablemetering cavity. The plug 31 comprises a plug sealing element 311,sealingly closing the metering cavity. The sealing element 311 isadvantageously made from an elastic thermoplastic polymer. The plungercan be manufactured e.g. by two component injection moulding of plungersealing element and plunger rod. In the longitudinal section given inFIG. 4(b), in which the valve seat 12 is shown, the radial opening 211in the cylinder head wall 21 is fluidly connected to inlet 121, whilethe outlet 122 is disconnected from the metering cavity.

The threaded 33 plunger shaft 32 is arranged in a distal (distal meaning“away from the valve, toward the drive unit”) threaded sleeve part 26 ofthe cylinder, where the outer thread 33 interacts with two inner threadsegments 23 of the threaded sleeve 26. The proximal cylinder part 22 andthe distal part/threaded sleeve 26 of the cylinder are attached togetherwith a suitable locking mechanism, for example by ultrasonic welding.Assembling the cylinder front two separate parts has the advantage thatthe single pieces are easier to manufacture. Furthermore it allowsoptimising of the materials used. The material of the proximal cylinderpart 22 can be chosen in regard to compatibility with medical liquidsand the interaction with the material of the plug sealing element 311.The material of the distal threaded sleeve 26 can be chosen in regard toa reliable thread interaction with the plunger shaft 32.

The plunger shaft 32 is provided with a longitudinal bore 322 along itsaxis, in which a rod of a plunger driving part (not shown) can bearranged. Four longitudinal cams or rips 34 are arranged along the bore322 of the plunger shaft, intended to interact with corresponding slotson the plunger driving rod. The cams 34 in at least one embodiment allowfor efficiently transmitting a rotational torque from the plungercoupler to the plunger. At the same time there is only low frictionalong the longitudinal axis 20.

The necessary bias force to remove tread lash is provided by a radialbias force element 5 in the form of a half-ring-like metal spring 52,having a flat portion 56 at one end of the spring 52, and a lockingstructure 53 on the other end. When mounted to the cylinder, the lockingstructure is arranged in a corresponding recession on the outer cylinderwall. The flat element 56 is arranged in an opening 221 in the threadedsleeve 26, and abuts the thread 33 of the plunger shaft 32.

During assembly, the spring element 52 may be slightly deformed. Whenthe locking structure 53 and the flat portion 56 snap into thecorresponding recessions and openings, the spring element is positivelylocked to the distal cylinder element, with a spring force due to theremaining radial deformation. Due to this remaining spring force theradial bias force element 5 generates a radial biasing force between thetwo inner thread segments 23 of the threaded sleeve 26 and the outerthread 33.

Since the bias spring element 52 in at least one embodiment has a verysimple structure and can be easily mounted to the cylinder, the dosingunit can be manufactured and assembled very efficiently. At the sametime the spring element provides a reliable and constant radial biasforce F_(bias). The spring element 52 may in at least one embodiment bemade from spring band steel, for example spring band steel 1.4310.

The use of two inner thread segments 23 in combination with a singlebiased flat surface element 56 is particularly advantageous, compared toa single threaded segment as described for FIG. 1. Since said two innerthread segments and the flat surface element provide a three-pointmounting (instead of two mounting points), the outer thread of theplunger shaft 32 is more stably mounted.

In at least one embodiment of a dosing unit is depicted in FIGS. 5 and26, where the embodiment has a radial bias force element 5. Here thespring element 52 is a metal spring having the basic shape of an openring, with two locking structures 53 at the two ends of the open ring,and a straight segment 56 in the middle. When mounted to the cylinder,the locking structures 53 are located in corresponding recessions. Thestraight segment 56 is located in an opening 221 of the cylinder wall,through which the flat portion 56 abuts the thread 33 of the plungershaft 32. The two arms of the spring element 52 between the lockingstructures 53 and the central flat portion 56 remain slightly deformedwhen mounted to the cylinder, providing a constant radial bias forceF_(bias).

In at least one embodiment plunger shaft 32 has been provided with acontinuous outer thread, while the inner thread has been reduced to asingle segment (FIG. 2) or two segments (FIG. 5). Such a configurationmay be advantageous in regard to reproducibility of thread lashreduction (see also discussion of FIGS. 2 and 3). Alternatively it isalso possible to provide the shaft 32 with a single outer thread segment22, and the inner surface of the cylinder with a continuous inner thread23, as for example shown in FIG. 6. The distal end of the plunger shaft32 is split into two shaft arms 321, 321′. On one shaft arm 321 a singleouter thread segment 33 is arranged, interacting width the inner thread23 of the cylinder. On the other shaft arm 321′ of the plunger shaft, aflat cylinder segment 56 is arranged, abutting the surface of the innerthread 23. A spring element 52 in the form of a single metal leaf springis arranged between the two shaft arms 321, 321′, providing a radialforce directed outwards. As a result the outer thread segment 23 isconstantly biased against the inner thread 23, thereby removing thethread lash. The two shaft arms 321, 321′ of the plunger as such are notbiased, since the corresponding force is provided by the spring element52. Thus such an embodiment does not suffer from creep deformation as inthe state of the art.

At least one additional embodiment of a plunger with thread lashreduction is given in FIG. 7. The outer thread 33 of the plunger shaftis divided into three rectangular portions 33 a, 33 a′, 33 a″, equallydistributed on the shaft 32. The threads are provided such that theouter thread is stably arranged and runs smoothly in a continuous innerthread of the cylinder. The thread portions are arranged incorresponding rectangular openings on the shaft, connected to the shaftonly by a longitudinal hinge structure 323, e.g. a film hinge or alongitudinal area with reduced wall thickness. The thread portions thusare pivotable along the axis of said hinges, abut a small angle. Thethree outer thread portions are radially biased toward the inner thread,thereby efficiently removing thread lash.

The necessary bias force can be obtained by one or more suitable springelements, e.g. a slotted metal ring spring (not shown) arranged in acircular groove in the bore 322 of the shaft. A suitable way tomanufacture such a plunger is insert injection moulding, where the ringspring is over-moulded with the thermoplastic polymer material of theplunger shaft.

In at least one additional embodiment, the dimensions of the shaft arechosen such that the pivotably mounted thread portions are slightlycompressed inwards when introduced into the inner thread. In that casethe spring force is generated by the shaft/thread structure itself.

At least one approach is shown in FIG. 8, where a plunger 3 having ashaft 32 with continuous outer thread 33 is arranged in a threadedsleeve 26 with four threaded claws 25, 25′, 25″, 25′″, separated byslots 251. In the given embodiment a slotted tension ring 27 is arrangedas a radial bias force element 5 around the distal end of the claws 26,Said tension ring is dimensioned such that the claws are slightly biasedinwards, toward the outer thread 33 of the plunger shaft, the inner andouter thread thereby engaging without thread lash.

At least one embodiment of a thread lash reducing arrangement withradial bias force is shown in FIG. 9. A sleeve element 263 is mounted tothe distal end of the cylinder 2. A radial bias force is provided byradial bias force element 5 with three spring biased inner threadsegments 59 a. The radial bias force element is mounted to the distalend of the sleeve element 263, and comprises a mounting sleeve 57 withthree openings 58, and three spring elements 59. Together the sleeveelement 263 and the radial bias force element 5 form a threaded sleeve26, the inner thread segments acting as the inner thread 23 of thethreaded sleeve.

Assembling the threaded sleeve 26, the mounting sleeve 57 is put overthe sleeve element 263, such that three protrusions 262 lock into theopenings 58, thereby positively locking the mounting sleeve 57 on thesleeve element 263. The three spring elements 59 are located in threelongitudinal slots 261 of the sleeve element 263.

Sleeve element 263 and bias force element 5 are designed such that thethread segments 59 a of the three spring elements 59 engage with theouter thread 33 of a plunger shaft 32 that is engaged with the threadedsleeve 26. The thread segments 59 a thus act as short thread segments 23of the threaded sleeve 26. In the assembled state, the thread segments59 a are radially biased, with a spring force F_(bias) acting radiallyinwards. The three spring elements are symmetrically arranged around thelongitudinal axis. As a result the radial force components acting on theplunger shaft stun to zero.

The flanks of the thread segments 59 a of the spring elements 59 of theradial bias force element 5 abut the flanks of the plunger shaft thread33. Thread lash is removed, similar to FIG. 2, as long as the relationF_(bias,min)=cot(α)F_(ax) applies for the minimum radial bias forceF_(bias,min) and the external axial force F_(ax).

In at least one embodiment, a similar radial bias force element 5 ismounted to the plunger shall, its spring biased outer thread segments 59b acting as the outer thread 33 of the plunger shaft, engaging with theinner thread 23 of the cylinder without thread lash.

In at least one embodiment of a thread lash reduction arrangement isdepicted in FIG. 10. In contrast to the embodiment shown in FIG. 3(a),where a radially biased inner thread segment provides the radial biasforce, a short wire segment 55 is used as the radial bias force element5.

The wire segment 55 is mounted on a threaded sleeve, parallel to theother threads 33 of the plunger. Two inner thread segments 23 arearranged on the sleeve 26 opposite to the wire 55. During operation thebias wire 55 is arranged in a groove of the outer thread 33. The wire isattached on its two ends to the sleeve in such a way that it is strainedwhen the plunger shaft tread 33 is introduced into the threaded sleeve26. The strained wire exerts a radial bias force on the plunger shaft,resulting in a radial bias force between outer thread 33 and threadsegments 23. In the embodiment as shown in FIG. 10(a), the wire abutsthe groove of the thread 33.

In at least one embodiment discussed so far the bias force providing thethread lash free engagement of plunger thread and cylinder thread wasdirected radially. Inner thread and outer thread were subject to a forceperpendicular to the longitudinal axis.

In at least one embodiment of the present disclosure, the bias force isdirected axially, along the longitudinal axis 20, as for example in FIG.11. A continuously threaded 33 plunger shaft 32 is arranged in athreaded sleeve 26 at the distal end of a cylinder. A separate threadedelement 64 with an inner thread 65 is coaxially mounted behind thethreaded sleeve 26, connected to the latter via a helical spring 62.

Together the threaded element 64 and the helical spring 62 act as aspring biased axial bias force element 6. The helical spring 62,arranged coaxially to the plunger 32, provides an axial force F_(bias),pushing the threaded element 64 away from the threaded sleeve 26 alongthe longitudinal axis 20. As a result, during normal operation thedistal flanks of the threaded portion 65 of the threaded element 64 abutthe proximal flanks of the plunger shaft thread 33, and the proximalflanks of the static threaded sleeve 26 abut the distal flunks of theplunger shall thread. Independently from any reversal of the rotationdirection of the plunger, or any external axial force due to a pressuredifferential in the metering chamber, the plunger 3 will be positivelylocked in the cylinder thread, without thread lash.

In at least one embodiment, the roles of the inner 23 and outer 33threads are exchanged, as shown in FIG. 11(c). A threaded sleeve 26comprises a continuous inner thread 23. A plunger shaft 32 is providedwith an outer thread 33. A threaded element 64′ with an outer thread 66is shiftably arranged on the plunger shaft 32. A spring element in theform of a helical spring 62 is coaxially arranged between the end of theouter thread portion 33 and the threaded element 64′. Together thethreaded element 64′ and the helical spring 62 form a spring biasedaxial bias force element 6. The helical spring 62 provides an axialforce F_(bias), pushing the threaded sleeve 64′ away from the outerthread portion 33 along the longitudinal axis 20. As a result, duringnormal operation the proximal flanks of the outer thread portion 66 ofthe threaded element 64′ abut the distal flanks of the cylinder thread23, and the distal flanks of the outer thread 33 abut the proximalflanks of the cylinder thread 23. Independently from any reversal of therotation direction of the plunger, or any external axial force, theplunger 3 will be positively locked in the cylinder thread 23, withoutthread lash.

In the dosing unit as known from prior art EP 2163273 A1, the frictionforce between cylinder valve member and plunger, which is necessary forreliably switching the valve before the plunger is linearly displaced,is constant. As a result the corresponding rotational torque that isnecessary for actuating the plunger is also constant.

To reduce energy consumption of the drive unit actuating the plunger,the friction force between cylinder valve element and plunger duringlinear plunger displacement may be reduced, where the valve is in one ofits operational states. At least one embodiment of a dosing unit thatallows controlling the friction between cylinder valve member 2 andplunger 3 is shown in FIGS. 12, 13, and 14. The valve seat of the dosingunit 1 is not shown for simplicity. The threads 33, 23 are onlyschematically indicated. The plunger 3 is coaxially arranged in thecylinder valve member 2, defining a metering cavity 11. The plunger 3comprises a plunger plug 31 and a plunger shaft 32. Said plunger shaftis longitudinally split into two shaft arms 321, 321′, pivotablyconnected to the plunger plug 31 by a hinge region 323. A couplerelement 4, releasably coupled to a drive unit (not shown) of an infusionpump device, has a driving rod 41, essentially comprising a distal partstem 412, to be connected to the drive unit, and a proximal part 411that is arranged in a longitudinal bore 322 of the plunger shaft. Theproximal part 411 comprises two cams 43, 43′, slidably arranged in theslot 37 that divides the shaft 32 into the two shaft arms 321, 321′.Rotational torque is primarily transferred from the driving rod 41 tothe plunger shaft 32 via said cams 43, 43′. Two other cams 44, 44′ arearranged perpendicular to the first cams 43, 43′, each having a longcut-out 441 that leaves a proximal ramp 71 and a distal ramp 71′.

Along each of the two shaft arms 321, 321′ a longitudinal slot 38 isarranged, on the proximal side limited by the hinge region 323 of theshaft 32, and on the other side by a bridge structure 39 bearing anouter thread element 33 a. 33 a′. The two bridge structures 39 comprisea proximal ramp 72 and a distal ramp 72′. When assembled the bridgestructures are arranged in the cut-out 441 of the coupling rid 41,between the two ramps 71, 71′. During operation the linear orientationof the driving rod 41 in regard to the cylinder valve member 2, as wellas the rotational orientation of the driving rod 41 in regard to theplunger 3, remain constant.

As will be shown, the elements of the plunger shaft 32 and the drivingrod 41 engage in such a way that friction between plunger and cylindervalve element is increased to a high value when the plunger shaft andthe driving rod are in certain positions to each other, therebyfrictionally coupling cylinder and plunger. In the other positionsfriction is on a lower level. This functional principle is explained inmore detail in FIG. 12, and Table 1.

TABLE 1 Frictional coupling between Plunger Cylinder valve rotationmember and direction Valve State Metering cavity plunger FIG. Pumpdirection Pump state Partially filled None 12(b) Pump direction Pumpstate Empty Yes 12(a) Refill direction Undefined, Empty Yes 12(a) valverotates until the other stopper is reached. Refill direction Refillstate Partially filled None 12(b) Refill direction Refill state MaximumYes 12(c) capacity Pump direction Undefined, Maximum Yes 12(a) valverotates capacity until the other stopper is reached. Pump direction Pumpstate Partially filled None 12(b)

Assuming that the valve of the dosing unit is in the pump state, thevalve member abutting a corresponding stopper of the valve seat, and theoutlet being connected to an infusion set, and that the metering cavityis partially filled (see the situation in FIG. 12(b)), the drive unitwill rotate the plunger such that it is linearly shifted to the left,thereby conveying liquid medicament toward the infusion set. Thefriction between plunger 3 and cylinder 2, namely thread friction andfriction between plunger plug and cylinder wall, is chosen such that isas small as possible, in order to minimize energy consumption of thedrive.

When the plunger reaches the cylinder head, and the metering cavity iscompletely emptied (see FIG. 12(a)), the proximal ramp 72 of the bridgestructure 39 of the plunger shaft 32, shifting to the left, engages withthe proximal ramp 71 of the driving rod 41 and forces the bridgestructure 39 radially outward toward the cylinder wall. As a result thethread segment 33 a on the bridge structure is radially pressed onto theinner thread 23, which increases thread friction until finally the outerthread is jammed in the inner thread.

To continue the administration of liquid medicament it will be necessaryto retrieve new liquid medicament from the primary reservoir of theinfusion pump. For that the valve has to be switched from the pump stateto the refill state, which requires a reversal of the rotation directionof the plunger and a frictional coupling between cylinder valve memberand plunger. Since the inner and outer threads are jammed, frictionbetween cylinder and plunger is considerably larger than frictionbetween cylinder and valve seat. The rotating plunger grips and rotatesthe cylinder in the valve seat until it reaches the stopper that definesthe valve's refill state, where the inlet conduit is connected to theprimary reservoir. Since cylinder rotation is now mechanically blocked,the drive unit can overcome the thread jamming. The proximal ramp 72 ofthe bridge structure 39, now shifting to the right, disengages from theproximal ramp 71 of the driving rod, until thread friction and thusenergy consumption is minimal again.

During the following refill mode, the plunger is displaced to the rightand the metering cavity is refilled (see FIG. 12(b)), until finallymaximum filling capacity is reached (see FIG. 12(c)). When the plungerreaches this maximum position at the right, the distal ramp 72′ of thebridge structure 39 engages with the distal ramp 71′ of the driving rod,forcing the bridge structure and the outer thread segment radiallyoutwards toward the inner thread 23, until the thread is jammed. Thevalve has now to be switched back to the pump position, disconnectingthe primary reservoir and connecting the infusion set. Since cylinderand plunger are again temporarily frictionally coupled, rotating theplunger in the reversed direction (pump direction) will rotate thecylinder in the valve seat until the stopper is reached that defines thepump state of the valve. Further rotation of the plunger disengages theramps 71′, 72′ and removes the thread jam, and the plunger can be movedagain to the left with minimum friction.

As can be seen, at least one embodiment of the dosing unit allowscontrolling the friction between plunger and cylinder valve member. Theinteraction between the ramps 72, 72′ of the bridge structures 39 andthe ramps 71, 71′ of the driving rod 41 provides the possibility oftemporarily radially biasing the outer thread segments toward the innerthread 23, thereby increasing thread friction. Thus a dosing unitoptimizes energy consumption by restricting friction to a minimum levelduring pumping and refilling. Although this increase may go up to anactual temporary jamming of the thread, it is also possible just toincrease friction to a value that is sufficient for the valve switching.

The example discussed above provides opportunities to switch the valveat two distinct positions, namely when the metering cavity is eithercompletely empty or completely full. An advantageous variant that allowsthe switching of the valve also in intermediate positions is explainedin FIG. 15. In addition to the two ramps 71, 71′ at the proximal anddistal end of the driving rod 41, two elevations 71 a arranged on thedriving rod between the ramps provide two other positions where bridgestructures 39 and thread segments 33 a, 33 a′ are radially biased (seeposition I). The height of the elevations is chosen such that althoughfriction is increased, no jamming takes place. Thus the dosing unit maycontinue in the mode it currently is in, for example pumping. The onlyeffect will be a temporary increase of energy consumption until the endof the elevation is reached, due to the temporary increase of threadfriction. If on the other hand the valve should be switched at thisintermediate position, the dosing unit may do so by reversing theplunger rotation and rotating the frictionally coupled cylinder in thevalve seat until the stopper is reached, and frictional coupling isreleased. Between the elevations and/or ramps, the bridge structure isnot biased (see position II). When the bridge structure reaches one ofthe outer ramps (see position III), the friction can be increased up tothread jamming, although this is not actually necessary.

The exemplary dosing units discussed in FIGS. 12 to 15 may also becombined with thread lash reduction. For example may the two shaft armsof the plunger shaft be pre-biased, due to radial dimensions that areslightly larger than the dimensions of the inner thread, or a radialbias force element as shown for example in the embodiments in FIG. 6 or7 can be applied.

At least one embodiment of a dosing unit 1 with controlled friction isshown in FIG. 16, with the valve seat not shown for simplicity. Thecylinder valve member comprises a cavity part 28 and a threaded sleevepart 26, mounted together. The threaded sleeve part 26 has an innerthread 23, which may be some few windings, or even only a threadsegment, particularly if one of the thread-lash reduction schemes isapplied that have been discussed further above.

The plunger 3 with plunger plug 31 and plunger shaft 32 is coaxiallyarranged in the cylinder 2. The plunger shaft 32 comprises a continuousouter thread 33, engaging with the inner thread 23 of the threadedsleeve 26. In the figure the threads are only schematically indicatedfor simplicity. The plunger shaft comprises a longitudinal bore 322, inwhich a driving rod 41 of a plunger driving pan 4 is shiftably arranged.

The plunger and the cylinder are realized in such a way that friction isminimal during the pump mode and refill mode, in order to restrictenergy consumption by the drive unit (not shown). In order totemporarily increase friction and thereby enabling the valve switchingfunctionality by the drive unit, two friction cylinders 74, 74′ arearranged on the proximal and the distal end of the plunger shaft 32.Said two friction cylinders may frictionally engage with twocorresponding hollow friction cylinders 74 a, 74 a′ that are arranged onthe proximal and the distal side of the inner thread 23 of the threadedsleeve 26. When the plunger is in the position where the metering cavity11 is completely empty (FIG. 16(a)) or completely filled (FIG. 16(b)),the abutting cylinder surfaces of the engaging friction cylinders causeincreased friction. This provides the necessary additional frictionbetween plunger and cylinder to reliably actuating the valve androtating the cylinder valve member in the valve seat upon reversal ofthe plunger rotation direction. This can be seen in more detail in FIG.16(c). When the spindle drive rotates the plunger toward the maximumdistal position, the friction cylinder 74 continuously shifts to theright into the cavity of the hollow friction cylinder 74 a, therebylinearly increasing friction. The dimensions of the interacting elementsand the materials used are chosen such that latest when the plunger isin the maximum filling position, the friction between cylinder valvemember and plunger, namely between the friction between the engagingfriction cylinders and the constant friction due to the thread and theplunger plug, are sufficiently large to actuate the cylinder valvemember in the valve seat when the plunger rotation direction isreversed.

When the plunger rotation direction is reversed, the plunger grips thecylinder and rotates it in the valve seat, until the cylinder abuts thestopper of the valve set. The static friction force is overcome, and theplunger starts again to rotate and to displace in the cylinder. Theoverlapping area of the friction cylinders, and thus the additionalfriction force, decreases linearly to zero.

As in the example discussed before, the friction between cylinder andplunger is mechanically controlled, depending on the relative positionof the plunger in the cylinder. However, the element controlling theadditional friction (the hollow friction cylinders 74 a, 74 a) are inthis case located on the cylinder, while in FIG. 12 the cams as thecontrolling element are located on the driving rod. In both cases therelative position of the linearly static elements (cylinder and drivingrod) in regard to the displaceable element (the plunger) is theparameter used to control the amount of friction between plunger andcylinder.

At least one embodiment of dosing unit 1, using a similar principle forcontrolling the friction, is described in FIG. 17. Again the valve seatis not shown for simplicity. Two stopper disks 73, 73′ are mounted onthe plunger shaft 32, on a proximal and a distal end of the continuousouter thread 33. The threaded sleeve 26 comprising the inner thread 23is also realized as a stopper disk 73 a.

The additional friction that is necessary for switching the valve in theend positions of the plunger is generated when one of the two stopperdisks, e.g. the proximal stopper disk 73 as shown in FIGS. 17(a) and(c), abuts the stopper disk 73 a mounted to the cylinder. Since theplunger is actually mechanically blocked front a further lineardisplacement, the thread friction force exponentially increases with anyfurther rotation, immediately jamming the plunger thread 33 in thecylinder thread 23 and frictionally coupling the plunger and thecylinder. When now the plunger rotation direction is reversed, thestatic friction between cylinder and plunger is large enough to actuateand rotate the cylinder in the valve seat (not shown) of the dosingunit. When the cylinder abuts the stopper of the valve seat the threadjamming is removed and frictional coupling is released. Thread frictionis back to a minimum level. A dosing unit embodiment as discussed in theexample above is very robust and reliable.

A further variant of such a dosing unit is shown in FIG. 18, having twostopper disks 73 a, 73 a′ mounted in the cylinder 2, while one stopperdisk 73 is mounted on the plunger shaft 32 on a distal end of thecontinuous outer thread 33, and located between the two other stopperdisks 73 a. 73 a′. The inner thread 23 of the cylinder is arranged onthe proximal stopper disk 73 a. Similar to the example above, thespindle thread 23, 33 jams when the central stopper disk 73 reaches oneof the peripheral stopper disks 73 a, 73 a′. The resulting frictionalcoupling between plunger and cylinder then allows rotating the cylinderand switching the valve when the rotation direction is reversed.

The inner thread 23 of the cylinder may also be arranged on the distalstopper disk 73 a′, when the outer thread 33 is arranged on the otherside of the central stopper disk 73. In such a case, however, thenecessary length of the plunger shaft and the driving rod, and thus theoverall length of the dosing unit, is increased.

Such a dosing unit can be further modified by arranging an outer thread33, 33′ on both sides of the central stopper disk, each engaging with aninner thread 23, 23′ on a stopper disk 73 a. 73 a′, as disclosed in FIG.19. The linear and angular orientation of the engaging threads isadvantageously realized in such a way that the two thread setslongitudinally bias each other, thereby effectively removing threadlash.

Instead of achieving the temporary locking of cylinder and plunger viajamming the spindle threads, as discussed above, it is also possible topositively lock the plunger and the cylinder at certain longitudinalpositions, as for example shown in the dosing unit in FIG. 20. Thecylinder 2 of the depicted embodiment comprises a cylinder part 28 and athreaded sleeve 26. The valve seat of the dosing unit, in which thecylinder valve member 2 is rotatably arranged, is not shown.

An embodiment of the threaded sleeve comprises a cylinder coupling part75 in the form of a circumferential ring with a multitude of lockingholes 751. Attached to a distal end of the plunger shaft 32, a plungercoupling part 76 is provided, having locking elements 761, 761′ in theform of spring biased balls, arranged on both sides of the cylinderlocking element 75. The plunger locking element 76 can be realized as acylinder-like element, having a multitude of circumferentiallydistributed locking elements 761, 761′, or as two or more arms bearingthe locking elements.

During pumping and refilling the position of the cylinder coupling partwith the multitude of locking holes 751 remains in a fixed position,since the cylinder remains in a fixed position. The plunger couplingpart 76 rotates and linearly shifts together with the plunger 3, towhich it is attached. When the plunger 3 arrives at one of its twoterminal positions, the spring-biased balls of one end of the plungerlocking structure start to slide and roll over the ring 75 surface, withminimum friction. However, when they finally arrive at theircorresponding locking holes 751, the balls 761, 761′ snap into the holesand positively lock the cylinder to the plunger. When now the plungerrotation direction is reversed, the plunger 3 actuates and rotates thecylinder valve member 2 in the valve seat, until the cylinder abuts thestopper of the valve seat. The valve has switched. Due to continuingrotation, the ball overcomes the spring force and slides under the ring65, and the temporary locking of cylinder and plunger is released.

FIG. 21 discloses another advantageous variant of a dosing unit 1, inwhich a cylinder coupling part in the form of a cylindrical sleeve 75 iscoaxially arranged on the cylinder part 28 and attached to the threadedsleeve 26. Alternatively said cylinder coupling part may also berealized as an integral part of the cylinder 28, or as a separate part.A plunger locking structure 76 that is attached to a distal end of theplunger shaft 32 comprises cams 762 that are pivotably mounted on thelocking structure 76, by pivot arms 763. Two sets of depressions 751,751′ are located on a proximal and a distal end of the cylinder couplingpart 75. The two coupling parts 75, 76 are realized in such a way thatthe cams 762 slide on the surface of the cylinder coupling part 75 whenthe cams are located between the two depressions 751, 751′, and snapinto the depressions when the plunger arrives at a terminal position,corresponding to an empty metering cavity 11 (FIG. 21(a)) or acompletely filled metering cavity (FIG. 21(b)). The cams are radiallybiased inwards, since the pivot arms 763 are deformed outwards when thecams slide on the surface during operation.

The depressions 751, 751′ are formed such that a perpendicular wall onthe outer side (toward the end of the dosing unit) provides a clearlydefined stopping position for the cam 762, thereby mechanically blockingthe further linear displacement of the cam and the attached plunger,which as a results leads to a thread jam. Plunger and cylinder are nowcoupled by static friction. Upon reversal of the plunger rotationdirection, the plunger rotates the cylinder and switches the valve. Whenthe valve has been switched and the further rotation of the cylindervalve member is blocked by a stopper of the valve seat, the thread jamis released, and plunger and cylinder are decoupled. An embodiment ofthe ramp, on the opposite side of the stopper wall of the depression,forces the pivotably mounted cam outwards, until it slides on thesurface. The plunger can now move to the other terminal position, withminimal friction.

At least one embodiment of a dosing unit is given in FIG. 22, where thepivotably mounted cam is replaced by a spring-biased ball as the lockingelement 761, mounted on the plunger locking structure 76. A number oflocking holes 751 are distributed on the cylinder coupling part 75 inthe form of a sleeve attached to the threaded part 26 of the cylinder.

During normal operation, in the pump mode or the refill mode, theplunger is linearly displaced along the axis, at the same time rotatingabout the axis. The spring-biased ball rolls and slides on the surfaceof the sleeve 75, providing minimum friction. At certain positions, thespring ball 761 snaps into a locking hole 751, positively lockingplunger and cylinder. However, since the valve is in a switched state,the cylinder being mechanically blocked from further rotation, the ballis immediately forced out of the hole upon further rotation of theplunger, and rolls and slides on the surface of the sleeve 75, providingminimum friction.

If on the other hand in such a position the rotation direction isreversed, the positive locking of cylinder and plunger is strong enoughto rotate the cylinder valve member in the valve seat, until the otherstopper is reached and further cylinder rotation is mechanicallyblocked. Again the ball is forced out of the hole upon further rotationof the plunger, and rolls and slides on the surface of the sleeve.

At least one advantage of such an embodiment is the possibility todefine intermediate positions on which the friction between plunger andcylinder is increased, and the valve can be switched. At these positionsof positive locking, the drive unit may or may not reverse the plungerrotation direction and thereby switching the valve.

In the embodiments of dosing units discussed so far the friction betweenplunger and cylinder valve member is may be controlled based on thelinear position of the plunger. Thus valve switching is enabled atcertain relative linear positions of the plunger within the cylinder.

At least one embodiment of a dosing unit achieves cylinder valve memberactuation by temporary frictional coupling between the cylinder and thedriving rod, upon each reversal of the rotation direction of the drivingrod. The coupling friction is nut controlled by the position of theplunger in the cylinder, but by the change of the driving rod rotationdirection and the relative angular orientation of cylinder and staticvalve seat. Such an embodiment may allow switching the valve at anylongitudinal position of the plunger.

An example of such an embodiment is given by the dosing unitschematically disclosed in FIG. 23. As can be seen in the schematiccross-section, a cylindrically shaped driving rod coupling part 77 isarranged coaxially to a cylindrically shaped cylinder coupling part 79.The driving rod coupling part 77 is attached to the driving rod (notshown) of the dosing unit, while the cylinder coupling part 79 isattached to the cylinder of the dosing unit (not shown). Thus duringoperation of the dosing unit, the two coupling parts 79, 77 rotate inregard to each other, while at the same time being fixed in regard toeach other in the longitudinal direction.

The coupling parts 79, 77 are coupled to each other by three frictionelements 770 attached to the driving rod coupling part 77, symmetricallydistributed along its circumference. The friction elements 770 have anO-like cross-section and are made from a flexible, elastic material. Thematerials of the friction elements 770 and the cylinder couplingelements 79 are advantageously chosen such that they provide a largestatic friction force.

The functional principle of the disclosed embodiment is that duringnormal operation of the dosing unit, where the plunger is eitheradvanced or retreated within the cylinder, the inner driving rodcoupling part 77 (attached to the rotating driving rod) rotatescounter-clockwise in regard to the cylinder coupling part 79 (attachedto the cylinder valve member), as shown in FIGS. 23(a) and (b). Thecylinder valve member is mechanically blocked from counter-clockwiserotation in the static valve seat, which is schematically shown by a cam29 of the cylinder abutting a stopper 123 of the valve seat. The elasticfriction elements 770 are deformed and are dragged along by the innercoupling part 77, sliding on the inner surface 792 of the outer cylindercoupling part 79, which results in a minimum sliding friction force.

For switching the valve, the rotation direction of the driving rod isreversed to clockwise. The deformed friction elements 770 are noworiented opposite in regard to the rotation direction (FIG. 23(c)). Thecylinder coupling part 79 is not mechanically blocked from clockwiserotation. The rotating driving rod coupling part 77 presses the frictionelements into the surface 792 of the coupling part 79 and jams them inregard to the coupling part 79. The resulting static friction forcebetween surface 792 and frictions elements 770 allows the inner couplingpart 77 gripping the outer coupling part 79 and rotating it clockwise inthe valve seat, until the cam 29 reaches the other stopper 123′ of thevalve seat, and is mechanically blocked again.

Since the cylinder coupling part cannot rotate any longer, the stillfrictionally coupled friction elements 770 of the inner coupling part 77are deformed, and flip via an intermediate state (FIG. 23(d)) to anopposite conformation (FIG. 23(e)). In this conformation the frictionelements again slide over the surface 792, with minimum slidingfriction.

To achieve high static friction, the materials of the friction elements770 and the surface 792 are chosen accordingly. For example may at leastone of said two elements be made or covered by a rubber-like material.Furthermore the elastic friction element is realized such that the forcenecessary to deform and flip the friction element is larger than theforce due to the torque between the inner and outer coupling parts 77,79. To adjust the friction forces in the given setup, the differentelements may be further modified. For example may the outer cylinder 79be provided with a roughened or teethed surface. The friction elementscan also be arranged on the cylinder coupling part 79 instead of thedriving rod coupling part 77, or on both parts.

At least one embodiment of a dosing unit having dynamic friction controlis disclosed in FIG. 24. Shown is the plunger driving part 4 of thedosing unit, having a driving rod 41 with four longitudinal cams 43. Ona distal end of the driving rod, opposite to the end that is to belocated in the longitudinal bore of a plunger shaft (not shown) of thedosing unit, a driving rod coupling part 77 is arranged, having the formof a disk. On the circumference of said disk 77, three mounting arms 776are provided, for attaching the plunger driving part 4 to a cylinder insuch a way that it is remains freely rotatable along the longitudinalaxis 20. The mounting arms 776 are provided with two distance rips 775and a cam 774.

During assembly the driving rod 41 is inserted into the plunger shaftbore. Forced by the ramp of the cam 774, the three mounting arms 776 areforced outwards, until a distal rim 222 of the cylinder wall snaps intothe gap provided between the cam 774 and the two distance rips 775. Thedimensions of the gap are chosen such that the rim and thus also thecylinder 2 is positively locked in regard to the plunger driving part 4with minimum play, but can be rotated around axis 20 with minimumfriction. The distal surface 792 of the cylinder rim also acts as thecylinder coupling part 79.

On the surface of disk 77 facing the cylinder, three friction elements770 are arranged, comprising a pivoting arm 771 that is connected to thedriving rod coupling part 77 by a hinge 772, and that has a tip 775facing the cylinder. The length of the friction element 770 is chosensuch that in the assembled state, during normal operation of the dosingunit, the arm 771 is tilted to one side away from the direction ofrotation, as shown in FIG. 24(d). The disk 77 rotates together with thedriving rod 41, symbolized by the arrow to the left. The cylinder 79 ismechanically blocked in the valve seat, symbolized by the crossed-outarrow to the left. During rotation of the driving rod, the lip 775 ofthe friction element 770 is dragged along and slides on the distalsurface 792 of the cylinder coupling part 79 with minimum friction.

In order to turn the cylinder valve member 2 in the valve seat and toswitch the valve, the rotation direction of the driving rod 41 isreversed. In this direction the cylinder 2 is not mechanically blockedin the valve seat. The friction element is now tilted toward thedirection of rotation (arrow to the right). Upon rotation of the drivingrod 41, the tip 775 of the friction element is pressed into the surface792 of the cylinder coupling part 79, jamming the frictional element 770(high static friction, gripping the cylinder and pushing it in the samerotation direction (FIG. 24(e)).

When the cylinder has rotated in the static valve seat for a certainrotation angle to the second stopper that corresponds to the other valvestate, further rotation of the cylinder is mechanically blocked. Forcedby the continuingly rotating driving rod 41 and disk 77, the hingeregion 772 of the friction element 77 is compressed (FIG. 24(f)),allowing the pivoting arm to flip to the other side (FIG. 24(g)). Thefriction element 770 is now again dragged along by the driving rodcoupling part, with minimum sliding friction.

Also in this embodiment of a dosing unit, the friction elements can bearranged on the cylinder coupling part 79 instead on the driving rodcoupling part 77, or on both parts. To increase friction, theinteracting elements 770, 792 may be modified. For example can thesurface 792 be provided with teeth that allow a stronger grip of the tip773 of the friction element 770, or the surface 792 can be provided withan adhesive or compressible coating. The use of teeth makes the couplingparts unsusceptible to contamination of the surfaces by oil or similarsubstances. At the same time the teeth define discrete steps of therotation angle.

In at least one embodiment shown in FIGS. 23 and 24, the driving rod,and not the plunger, actuates the cylinder valve member in the valveseat. To avoid that the plunger already gets linearly displaced duringthe valve switching process, the coupling between plunger shaft anddriving rod is advantageously temporarily released during valveswitching. This is achieved by realizing the longitudinal bore 322 andthe driving rod 41 with a certain predefined play. In such an embodimentthere is a reduction of friction between driving rod and plunger shaftduring linear displacement.

FIG. 25 depicts in a cross-sectional view different variants ofinteracting plunger shafts 32 and driving rods 41. In FIG. 25(a), thelongitudinal bore of the plunger shaft 32 has essentially the shape ofthe driving rod 41, the four longitudinal cams 43 of the driving rodbeing slidably arranged in corresponding slots of the longitudinal bore.Such an embodiment provides essentially no rotational play betweendriving rod and plunger shaft, and is advantageously used for dosingunits as for example shown in FIGS. 14 to 22.

In FIG. 25(b), the longitudinal bore of the plunger shaft 32 providesrotational play. The slots between the cams 34 of the plunger shaft aredesigned such that upon reversal of the rotation direction of thedriving rod, in the given Figure from clockwise to counter-clockwise,for a certain predefined rotation play angle α, the cams 43 do notrotationally engage with the cams 34 of the plunger rod, until the cams43 have reached the cants 34 on the other side of the slot (FIG. 25(c)).The angle α is chosen such that the friction elements 770 of FIG. 23 or24 can completely switch before the driving rod 41 and the plunger shalt32 rotationally engage again. This ensures that in a dosing unit as forexample shown in FIGS. 23 and 24, the friction element does not remainfor a longer time in an intermediate state (FIGS. 23(d), 24(f)), whichcould lead to irreversible deformation.

In at least one embodiment, as shown in FIG. 25(d), the predefinedrotation angle β is chosen larger than the angle that is necessary forswitching the valve. This ensures that it is geometrically impossible toresume plunger displacement before the valve has been switched.

At least one embodiment of dosing unit 1 is disclosed in FIG. 26. Thecylinder 2 and the plunger (not visible) are identical to the embodimentshown in FIG. 5. Visible is the threaded sleeve part 26 of the cylinder2, with the radial bias force element 5 mounted to the threaded sleevepart. A plunger driving part 4 similar to the one shown in FIG. 5 isattached to the distal end of the threaded sleeve part 26 with threemounting arms 776. The driving rod coupling part 77, to which thedriving rod (not visible) and the friction elements 77 are mounted,provides additional functionality.

The friction elements 770/pivoting arms 771 are attached to the drivingrod coupling part 77 by hinge structures 772, which are mounted tospring element structures 777. Said spring element structures 777provide certain elasticity and flexibility in the longitudinal andradial direction.

The distal end of the coupling part 77, opposite to the driving rod andfacing toward the driving unit (not shown), is realized as a concave,self-centering drive unit coupling 42, with three protruding cams 421that are intended to engage with corresponding elements of the driveunit.

In FIG. 26 the friction elements 770 are shown in the intermediatestate, as shown in FIG. 24(f). FIG. 27 shows the different steps duringvalve switching. Only the most distal end of the cylinder 2 is shown.The depicted different steps are as follows:

-   I: The valve is in a first valve state. The driving rod coupling    part 77 with the piston rod (not visible) is in the    counter-clockwise freewheel mode, and the friction elements 770 are    dragged along the surface 792 of the rim 222. The plunger (not    shown) is linearly displaced, driven by the rotating driving rod.-   II: The plunger (not visible) has reached a stop position    (completely empty or completely full), or the control system of the    dosing unit decides to switch the valve for another reason.-   III: The valve switching process begins. The rotation direction is    reversed from counter-clockwise to clockwise. The friction elements    jam with the surface of the rim of the cylinder, and actuate the    cylinder clockwise in the valve seat.-   IV: The cylinder valve member, rotating in the valve seat (not    shown) reaches the stopper (not shown) that defines the second valve    position. The valve has been switched to its second state.-   V: The cylinder valve member is blocked from further rotation.-   VI: Upon further rotation of the driving rod, the friction elements    flips over, and the jamming between driving rod and cylinder valve    member is released.-   VII: The valve is in the second valve state. The driving rod    coupling part with the piston rod (not visible) is in the clockwise    freewheel mode. The friction elements are dragged along the surface    of the rim. The plunger (not shown) is linearly displaced upon    rotation of the driving rod.-   VIII: The plunger (not visible) has reached the other stop position    (completely full or completely empty), or the control system of the    dosing unit decides to switch the valve for another reason.-   IX: The valve switching process begins. The rotation direction is    reversed from clockwise to counter-clockwise. The friction elements    jam with the surface of the rim of the cylinder, and actuate the    cylinder clockwise in the valve sear.-   X: The cylinder valve member, rotating in the valve seat (not shown)    reaches the stopper (not shown) that defines the first valve    position. The valve has been switched to its first state.-   XI: The cylinder valve member is blocked from further rotation.-   XII: Upon further rotation of the driving rod, the friction elements    flips over, and the jamming between driving rod and cylinder valve    member is released.-   XIII: The valve is in the first valve state again. The driving rod    coupling part with the piston rod (not visible) is in the    counter-clockwise freewheel node. The friction elements are dragged    along the surface of the rim. The plunger (not shown) is linearly    displaced upon rotation of the driving rod. Step XIII is essentially    identical to step 1, except for the angular orientation of the    driving rod.

In at least one dosing unit is schematically depicted in FIG. 28, wherea controlled coupling between cylinder 2 and driving rod 41 is realizedwith a bistable ratchet mechanism 78. All figures are shown with thecylinder valve member remaining static, and the driving rod 41 and valveseat moving in relation to the cylinder valve member.

A cog wheel 781 is mounted on the driving rod 41 at a distal end. Adouble pawl element 785 with two opposite pawls 787, 787′ is pivotablymounted on an axis bearing 784, which itself is mounted on the cylindervalve member 2. The double pawl element 785 is provided with an arm 788.A tension spring 786 is arranged between a first suspension point at theend of the arm and a second suspension point 783. To provide symmetricaloperational conditions, said second suspension point 783 has to belocated somewhere on a straight line through the driving rod's rotationaxis and the pivotal axis 784 of the double pawl element 785.

In FIG. 28(a) the driving rod 41 is in the counter-clockwise freewheelmode (symbolized by an arrow). The plunger can be linearly displaced inthe corresponding direction. The bistable ratchet mechanism is in one ofits stable states, driven by the spring force of the tension spring 786.The teeth 782 of the cog wheel 781, rotating counter-clockwise togetherwith the driving rod, can pass the pawl 787 without switching theratchet mechanism.

For switching the valve, the rotation direction of the driving rod 41 isreversed, in the given case from counter-clockwise to clockwise (FIG.28(b). The tooth right of the pawl 787′ abuts the pawl, and the ratchetis jammed. The driving rod 41 and the cylinder valve member 2 are nowrotationally coupled via the pawl 787 and the bearing axis 784, and therotating driving rod rotates the cylinder valve member clockwise (dashedarrow).

The rotation of the cylinder is stopped when a first switching element124 mounted to the valve seat (dotted arrow) reaches the bistableratchet mechanism, as shown FIG. 28(c). The switching element 124 pushesthe first pawl 787 toward the cogwheel. The double pawl element 785pivots around the axis bearing 784, the tension spring 786 is expanded,and when the arm 788 passes the line defined by suspension point 783 andaxis bearing 784, the bistable ratchet switches to the other state. Thecylinder valve member 2 is now rotationally decoupled from the drivingrod 41. The driving rod 41 is in the clockwise freewheel mode again. Theteeth of the cogwheel can pass the ratchet mechanism without engaging,and the plunger is linearly displaced in the opposite direction.

To switch the valve back to the first state, the process is repeated(FIG. 28(d)), by reversing the rotation direction from clockwise tocounter-clockwise. The ratchet and the cogwheel jam, rotationallycoupling the cylinder valve member and the driving rod. The driving rodrotates the cylinder valve member counter-clockwise, until the secondswitching element 124′ mounted to the valve seat reaches the ratchetmechanism, and flips over the double pawl element to its first state, asshown in FIG. 28(a), thereby decoupling again the cylinder valve memberand the driving rod.

The angular position of the switching elements 124, 124′ is chosen suchthat the ratchet switching positions correspond to the two valvepositions. Thus no additional stopper elements are necessary, delimitingthe rotation of the cylinder valve member in the valve seat.Advantageously they are nevertheless provided, to define clear valve endpositions.

Instead of using a separate cogwheel the driving rod itself may be usedas the cogwheel, with its cams 43 acting as the teeth, if a sufficientnumber of cams 43 are provided to realize the ratchet mechanism.

At least one embodiment of a controllable coupling between driving rod41 and cylinder valve member 2 is disclosed in FIG. 29. A driving rod 41is arranged within the cylinder 2, operationally engaging with theplunger shaft (not visible). Only the distal end 412 of the driving rodis visible in FIG. 29(a). The driving rod is provided with a driving rodcoupling part 77, in the form of a hollow cylinder 778. The distal endof the cylinder is provided with a cylinder coupling part 79, intendedto be arranged in the hollow cylinder 778. The cylinder coupling part 79comprises two clamp arms 793, 793′ that are pivotably connected to thecylinder 2 via hinges 794, 794′. One clamp arm 793 has one clamp finger795, having a radial protrusion on the outside toward the inner side ofthe hollow cylinder 778. The other clamp arm 794′ has two clamp fingers795′ with a radial protrusion. Alternatively both clamp arms may beprovided with an equal number of clamp fingers.

The dimensions of the two coupling parts 79, 77 are chosen such that inthe assembled state of the dosing unit the clamp fingers 795, 795′ areradially biased against the inner surface of the hollow cylinder 778. Asa result the driving rod 41 and the cylinder valve member 2 arefrictionally coupled, the rotating driving rod being able to actuate thecylinder valve member.

To minimize friction during the linear displacement of the plungerwithin the cylinder, the cylinder coupling part 79 is provided withmeans 796, 796′ to rotationally decouple the two coupling parts 79, 77.Each of the two clamp arms is provided with a release element arranged796, 796′ outside of the hollow cylinder 778. Two switching elements(nor visible) mounted on the valve seat are arranged on such angularpositions that in each of the two valve states, one of the switchingelements engages with one of the decoupling elements 796, 796′. Theresulting force presses the corresponding clamp arm 793, 793′ inwards,thereby decoupling the two coupling parts 79, 77, and thus the drivingrod 41 and the cylinder valve member 2. Upon further rotation of thedriving rod in the same direction, friction is minimal, and the cylindervalve member remains on place.

To switch the valve, the rotation direction of the driving rod isreversed. The switching element disengages the release element, and theclamp arms engage again with the hollow cylinder. The frictionallycoupled cylinder valve member rotates together with the driving rod,until the second switching element reaches the second release element,and coupling element and driving rod are decoupled again.

Instead of coupling arms engaging with a hollow cylinder, anotherembodiment of such a controllable coupling can be realised with a coiledspring, connected to the cylinder. The coil spring is looped around acylindrical portion of the driving rod, and frictionally couples thecylinder and the driving rod. Switching elements of the valve seat canengage with the ends of the coil spring, increasing the radius of thecoil spring and temporarily decoupling cylinder and driving rod.

While various embodiments of dosing units and methods for their use havebeen described in considerable detail herein, the embodiments are merelyoffered by way of non-limiting examples of the disclosure describedherein. It will therefore be understood that various changes andmodifications may be made, and equivalents may be substituted forelements thereof, without departing from the scope of the disclosure.Indeed, this disclosure is not intended to be exhaustive or to limit thescope of the disclosure.

Further, in describing representative embodiments, the disclosure mayhave presented a method and/or process as a particular sequence ofsteps. However, to the extent that the method or process does not relyon the particular order of steps set forth herein, the method or processshould not be limited to the particular sequence of steps described.Other sequences of steps may be possible. Therefore, the particularorder of the steps disclosed herein should not be construed aslimitations of the present disclosure. In addition, disclosure directedto a method and/or process should not be limited to the performance oftheir steps in the order written. Such sequences may be varied and stillremain within the scope of the present disclosure.

Having described the present disclosure in detail and by reference tospecific embodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of thedisclosure defined in the appended claims. More specifically, althoughsome aspects of the present disclosure are identified herein aspreferred or particularly advantageous, it is contemplated that thepresent disclosure is not necessarily limited to these preferred aspectsof the disclosure.

LIST OF REFERENCE NUMERALS

-   1 dosing unit-   11 metering cavity-   12 valve seat-   121 inlet-   122 outlet-   123, 123′ stopper elements-   124, 124′ switching element-   2 pump cylinder/cylinder valve member-   20 cylinder axis-   21 cylinder head-   211 opening-   212 guide ring-   22 cylinder wall-   221 opening in the cylinder wall-   222 rim-   23, 23′ threaded portion of the cylinder, cylinder thread-   25, 25′, 25″, 25′″ threaded claw-   251 slot-   26 threaded sleeve par-   261 slot-   262 protrusion-   263 sleeve element-   27 tension ring-   271 slot-   28 cavity part-   29 cam-   3 plunger-   31 plunger plug-   311 plug sealing element-   312 plug protrusion-   32 plunger shaft-   321, 321′ shaft arm, split portion of plunger shaft-   323 hinge-   322 longitudinal bore-   33, 33′ threaded portion of the plunger, plunger thread-   33 a, 33 a′, 33 a″ portions of the thread-   331 lateral surface of the thread-   34 cam-   35 plunger coupling element-   37 slot-   38 slot-   39 bridge structure-   4 plunger driving part-   41 plunger driving rod-   411 proximal part-   412 distal part-   42 drive unit coupling-   421 cam-   43, 43′ cam-   44, 44′ cam-   441 cut-out-   5 radial bias force element-   51 threaded element-   52 spring element-   53 locking structure-   55 wire-   56 flat surface element-   57 mounting sleeve-   58 opening-   59 spring element-   59 a inner thread segment-   59 b outer thread segment-   6 axial bias force element-   62 spring element-   64, 64′ threaded element-   65 inner thread portion of threaded element-   66 outer thread portion of threaded element-   7 friction control element-   71, 71′ ramp-   71 a elevation-   72, 72′ ramp-   73, 73′ stopper disk-   73 a, 73 a′ stopper disk-   74, 74′ friction cylinder-   74 a, 74 a′ friction cylinder-   75 cylinder coupling part-   751 locking hole-   76 plunger coupling part-   761, 761′ spring-biased ball, locking element-   762 cam, locking element-   763 pivot arm-   77 driving rod coupling part-   770 friction element-   771 pivoting arm-   772 hinge-   773 tip-   774 snap lock cam-   775 distance rip-   776 mounting arm-   777 spring element-   778 hollow cylinder-   78 bistable ratchet mechanism-   781 cog wheel-   782 tooth-   783 suspension point-   784 axis bearing-   785 double pawl element-   787, 787′ pawl-   786 tension spring-   788 arm-   79 cylinder coupling part-   792 surface-   793, 793′ clamp arm-   794, 794′ hinge-   795, 795′ clamp finger-   796, 796′ release element-   F_(bias) bias force-   F_(bias,ax) axial component of the bias force-   F_(ax) axial force acting on the plunger

1. A dosing unit for an infusion pump device, the dosing unitcomprising: a piston pump with a pump cylinder; a plunger arrangedwithin the pump cylinder, the pump cylinder and the plunger coaxiallyarranged along a longitudinal axis; and a separate bias force element;wherein the plunger has a plunger shaft with a plunger thread and thepump cylinder has a threaded sleeve part with a cylinder thread; whereinone of the plunger thread or cylinder thread is an outer thread and theother one is an inner thread, the inner thread and outer thread engagingwith each other in such a way that a rotational movement of the plungeraround the longitudinal axis results in a linear displacement of theplunger along the longitudinal axis; and wherein the separate bias forceelement that biases the two threads in regard to each other along thelongitudinal axis, such that the threaded engagement of the inner threadand the outer thread is free of play independent of a direction of arotational movement and linear displacement of the plunger in regard tothe cylinder.
 2. The dosing unit of claim 1, wherein the plunger threadis the outer thread and the cylinder thread is the inner thread.
 3. Thedosing unit of claim 1, wherein the separate bias force element subjectsthe plunger shaft to a force perpendicular to the longitudinal axis,thereby pressing a portion of the plunger thread onto a portion of thecylinder thread.
 4. The dosing unit of claim 3, wherein the separatebias force element comprises a radially biased flat surface that abutsthe lateral surface of the outer thread.
 5. The dosing unit of claim 1,wherein one or more portions of the cylinder thread or the plungerthread are pivotably mounted on the cylinder, or on the plunger shaft,respectively.
 6. The dosing unit of claim 5, further comprising a springelement, wherein the spring element radially biases the pivotablymounted thread portions toward the other thread.
 7. The dosing unit ofclaim 1, wherein the separate bias force element comprises a tensionedsegment of wire that is mounted to the cylinder or the plunger and isarranged in such a way that it is located in a groove segment of theouter thread and exercises a bias force perpendicular to thelongitudinal axis.
 8. The dosing unit of claim 1, wherein the bias forceelement comprises a threaded element, which is coaxially mounted on thethreaded sleeve part or on the plunger shaft, and is longitudinallyshiftable in regard to the first threaded sleeve or the plunger shaft,respectively; which has a thread portion engaging with the plungerthread or the cylinder thread, respectively; and which has a springelement that subjects the threaded element to an axial bias force inregard to the first threaded sleeve or the plunger shaft, respectively.9. The dosing unit of claim 1, wherein the bias force element comprisesone or more spring elements with inner or outer thread segments, suchthat the inner or outer thread segments are radially biased toward theouter or inner thread, and wherein the inner or outer thread segmentsact as the inner or outer thread, respectively.
 10. The dosing unit ofclaim 1, wherein the bias force element is elastic.
 11. The dosing unitof claim 1, wherein the bias force element is made from a material thatis different from the material of the cylinder and/or the plunger. 12.The dosing unit of claim 1, wherein the bias force element is made frommetal, and/or the cylinder and/or the plunger is made from polymer. 13.The dosing unit of claim 1, further comprising a plunger driving partprovided for transmitting rotational torque from a driving unit to theplunger without itself being linearly displaced, the cylinder, theplunger and the plunger driving part being coaxially arranged along alongitudinal axis and rotatable around said axis in regard to staticparts of the dosing unit; and wherein the plunger driving part has adriving rod that is arranged in a longitudinal bore of the plungershaft, the driving rod being linearly displaceable within thelongitudinal bore along the longitudinal axis, and being rotationallyengaged with the plunger shaft.
 14. The dosing unit of claim 13, furthercomprising one or more first coupling parts mounted to or being integralwith the cylinder, and one or more second coupling parts mounted to orbeing integral with the plunger driving part and/or the plunger; thefirst and second coupling parts interacting in such a way that upon areversal of the rotation direction of the plunger driving part thecylinder is rotationally coupled to the plunger driving part if it waspreviously not rotationally coupled, and vice versa; and/or one or morefirst coupling parts mounted to or being integral with the cylinderand/or the plunger driving part, and one or more second coupling partsmounted to or being integral with the plunger driving part and/or theplunger; the cylinder being rotationally coupled to the plunger oncertain linear positions of the plunger in regard to the cylinder andbeing not rotationally coupled to the plunger on the other position. 15.The dosing unit of claim 14, wherein the one or more first couplingparts are mounted to or integral with the cylinder, and the one or moresecond coupling parts are mounted to or integral with the plungerdriving part and/or the plunger; wherein the first and second couplingparts interact in such a way that the first and second coupling partsare bidirectionally switchable between a first state and a second state,by reversing the rotation direction of the plunger driving part; thefirst and second coupling parts are unidirectionally switchable from thefirst state to the second state, by mechanically blocking cylinderrotation or actuating the first coupling part; and the cylinder isrotationally coupled to the plunger driving part in the first state ofthe first and second coupling parts; and not rotationally coupled in thesecond state.
 16. The dosing unit of claim 14, wherein the one or morefirst coupling parts are mounted to or being integral with the cylinderand/or the plunger driving part, and wherein the one or more secondcoupling parts are mounted to or being integral with the plunger drivingpart and/or the plunger; the first and second coupling parts interactingin such a way that the cylinder is rotationally coupled to the plungeron certain linear positions of the plunger in regard to the cylinder andis not rotationally coupled to the plunger on the other positions. 17.The dosing unit of claim 14, wherein the one or more first couplingparts are mounted to or being integral with the cylinder, and the one ormore second coupling parts are mounted to or being integral with theplunger driving part; the first and second coupling parts interacting insuch a way that the cylinder is rotationally decoupled from the plungerdriving part on certain angular orientations of the cylinder in regardto static parts of the dosing unit, and is rotationally coupled on theother orientations.
 18. The dosing unit of claim 15, wherein the one ormore first coupling part is mounted to or being integral with thecylinder, and the one or more second coupling part is mounted to orbeing integral with the plunger driving part; wherein the first and/orthe second coupling parts comprise one or more bistable elements thatcan be in a first configuration where the bistable elements rotationallycouple the first and second coupling parts by static friction orpositive locking when the plunger driving part rotates clockwise, and donot rotationally couple the first and second coupling parts when theplunger driving part rotates counterclockwise; and in a secondconfiguration where the bistable elements rotationally couple the firstand second coupling parts by static friction or positive locking whenthe plunger driving part rotates counterclockwise, and do notrotationally couple the first and second coupling parts when the plungerdriving part rotates clockwise.
 19. The dosing unit of claim 18, whereinthe one or more bistable elements are friction elements that areswitchable between two configurations, and that the rotational couplingis a static frictional coupling.
 20. The dosing unit of claim 19,wherein the one or more bistable friction elements are switchablebetween the two configurations by reversing the rotation direction ofthe plunger driving part in case the first and second coupling parts arenot rotationally coupled; and by reversing the rotation direction of theplunger driving part and blocking cylinder rotation in case the firstand second coupling parts are rotationally coupled.
 21. The dosing unitof claim 20, wherein cylinder rotation is blocked on certain angularorientations of the cylinder in regard to the static parts of the dosingunit.
 22. The dosing unit of claim 15, wherein the one or more bistableelements are ratchet mechanisms that are switchable between twoconfigurations, and that the rotational coupling is engaged when theratchet mechanism is locked.
 23. The dosing unit of claim 22, whereinthe one or more bistable ratchet mechanisms are switchable between thetwo states by reversing the rotation direction of the plunger drivingpart in case the ratchet mechanism is locked; and by reversing therotation direction of the plunger driving part (and additionallyactuating the ratchet mechanism in case the ratchet mechanism is notlocked.
 24. The dosing unit of claim 23, wherein the ratchet mechanismis actuated by switching elements mounted to or being integral with thestatic parts of the dosing unit.
 25. The dosing unit of claim 16,wherein the one or more first coupling parts comprise first rampsprovided on the plunger driving rod, and the one or more second couplingparts comprise second ramps provided on a structure pivotably mounted onthe plunger shaft, the structure carrying portions of the outer thread;wherein the first and second ramps are arranged such that on at leastone linear position of the plunger in regard to the cylinder some of thefirst ramps abut some of the second ramps, and press the outer threadportions radially outwards onto the inner thread of the cylinder,thereby frictionally coupling the cylinder and the plunger.
 26. Thedosing unit of claim 16, wherein the one or more first coupling partsare first friction elements mounted to or being integral with thecylinder, and the one or more second coupling parts are second frictionelements mounted to or being integral with the plunger, wherein atcertain longitudinal positions of the plunger in regard to the cylinderone of the first friction elements frictionally engages with one of thesecond friction elements, thereby frictionally coupling the cylinder andthe plunger.
 27. The dosing unit of claim 26, wherein the one or morefirst friction element is a hollow cylinder, and the one or more secondfriction element is a friction cylinder, which frictionally engages withthe hollow cylinder when the friction cylinder is located in the hollowcylinder.
 28. The dosing unit of claim 16, wherein the one or more firstcoupling parts are first stopper elements mounted to or being integralwith the cylinder, and the one or more second coupling parts are secondstopper elements mounted to or being integral with the plunger, whereinin at least one longitudinal position of the plunger in regard to thecylinder one of the first stopper elements abuts with one of the secondstopper elements, thereby blocking the further linear displacement ofthe plunger, and releasably jamming the inner thread of the cylinder andthe outer thread of the plunger.
 29. The dosing unit of claim 28,wherein the stopper elements are disks.
 30. The dosing unit of claim 16,wherein the one or more first coupling part is a cylinder coupling partand the one or more second coupling part is a plunger coupling part,wherein the cylinder coupling part comprises first locking elements andthe plunger coupling part comprises second locking elements, whichreleasably lock the plunger to the cylinder at certain longitudinalpositions of the plunger in regard to the cylinder.
 31. The dosing unitof claim 17, wherein the one or more first coupling part is mounted toor being integral with the cylinder, and the one or more second couplingpart is mounted to or being integral with the plunger driving part,wherein the two coupling parts are frictionally coupled, and wherein thefrictional coupling is releasable by switching elements mounted to orbeing integral with the static parts of the dosing unit.
 32. A dosingunit for an infusion pump device, the dosing unit comprising: a pistonpump including a pump cylinder, wherein the pump cylinder has a cylinderthread, a plunger coaxially arranged within the pump cylinder along alongitudinal axis, wherein the plunger has a plunger shaft with aplunger thread engaging the cylinder thread to cause linear displacementof the plunger along the longitudinal axis when the plunger is rotatedaround the longitudinal axis, and a bias element applying a biasingforce between the cylinder thread and the plunger thread transversely tothe longitudinal axis to reduce play between the cylinder thread and theplunger thread.
 33. The dosing unit of claim 32, wherein the biaselement includes a spring.
 34. The dosing unit of claim 33, wherein thespring is a helical spring.
 35. The dosing unit of claim 33, wherein thespring has an open ring shape.
 36. The dosing unit of claim 35, whereinthe spring has a locking structure at one end configured to secure thespring to the piston pump and a flat portion at the other end abuttingagainst the plunger thread.
 37. The dosing unit of claim 35, wherein thespring a locking structure at both ends configured to secure the springto the piston pump and a straight element between the ends abuttingagainst the plunger thread.
 38. The dosing unit of claim 33, wherein theplunger shaft includes at least two shaft arms with the spring disposedin between.